The identity of the attacker has not been released. British Prime Minister Theresa May said Thursday that the man was British-born and had previously been investigated by intelligence services for links to extremism, but had been determined to be a peripheral figure.

“Our working assumption is that the attacker was inspired by Islamist ideology,” she told members of Parliament.

The chaos unfolded on the Westminster Bridge near the Parliament building when an SUV mowed down pedestrians on the bridge. London metro police counterterrorism Chief Mark Rowley said that 29 people were hospitalized and seven were in critical condition.

May called the attack a “sick and depraved” act, but did not elevate the terror threat level, which was already at severe.

Three civilians were among those killed. Rowley identified the officer as Keith Palmer, 45, who had served as an officer for 15 years.

“Yesterday we saw the worst of humanity. But we will remember the best,” May said Thursday. “We will remember the exceptional bravery of our police, security and emergency services.”

Rowley said Wednesday it was still “too early” to release the name of the attacker, but added that officials “think we know who the attacker is and are working to establish who his associates are.”

Armed and unarmed patrols have been stepped up as a precaution across the country, he said.

May said that as the British go on about their daily lives, it shows that in the “millions of acts of normality that we find the best response to terrorism.

The greatest response lies not in the words of politicians but the everyday actions of ordinary people,” she said.